The birth of a world-changing idea, relativity, and how it was shaped by the social upheaval and bloody horror of the First World War Einstein's ascent to worldwide celebrity was, in large part, not his own doing. It was because of two wars. The first was the Great War, the industrialized slaughter that bled Europe from 1914 to 1918. While Einstein never held a rifle, the war shaped his life and work for years: falling ill from wartime starvation, unable to communicate with his most important colleagues. Being a scientist trapped one in the power plays of empire. The second conflict was Einstein's struggle to craft relativity and persuade the world that it was correct. This was, after all, the first complete revision of our conception of the universe since Isaac Newton's. Its victory was far from sure. Scientists seeking to confirm Einstein's ideas were arrested as spies. Technical journals were banned as enemy propaganda. Colleagues died in the trenches. In Berlin, Einstein was separated from his most crucial ally by barbed wire and U-boats. This ally was the Quaker astronomer and Cambridge don A. S. Eddington, who would go on to convince the world of the truth of relativity and the greatness of Einstein. In May of 1919, when Europe was still in chaos from the war, Eddington led a globe-spanning expedition to catch a fleeting solar eclipse for a rare opportunity to confirm Einstein's bold prediction that light has weight. It was the result of this expedition--the proof of relativity, as many saw it--that put Einstein on front pages around the world. Precisely one hundred years later, Einstein's War is a celebration of how bigotry and nationalism can be defeated and of what science can offer when they are.